Video by ScooterLab.UK via YouTube
Source
A ScooterLab.UK tutorial to repair a Vespa PX or large-frame gear selector box.
Why repair rather than buy new? Firstly many of the new spare parts available are rubbish, and secondly, this mod makes the box more durable than it was when it was new.
Warning: you will need access to a MIG welder and pillar drill, or someone who can do those jobs for you.